Portable grinding machine



Aug. 21, 1962 E. MURscHEL.

PORTABLE GRINDING MACHINE Filed April 5, 1960 .m RC mw WM /W [111, nrraRNEJ United States Patent 3,049,842 PORTABLE GRINDING MACHINE Erwin Murschel, Stuttgart-Weilimdorf, Germany, assignor to C. F. Scheer & Cie., Stuttgart-Feuerbach, Germany Filed Apr. 5, 1960, Ser. No. 20,199 Claims priority, application Germany Apr. 23, 1959 6 Claims. (Ci. 51-170) The present invention relates to improvements in portable grinding and polishing machines, and more particularly to a portable grinding machine in which the abrading member consists of `an endless liexible belt.

An important object of the present invention is to provide a portable grinding machine with a low center of gravity which insures better guidance of the machine along a workpiece Without it being necessary that the machine be equipped with a special guide frame such as is utilized in certain types of known portable grinding, sanding, polishing and like machines.

Another important object of the invention is to provide a portable grinding or polishing machine of the above outlined characteristics wherein the endless abrading member is mounted on large-diameter wheels whereby the abrading member need not be subjected to excessive tension such as would reduce its useful life.

A further object of the invention is to provide a grinding or polishing machine of of the above outlined characteristics in which .the abrading member is not subjected to excessive deections about small-diameter guiding and driving members such as would contribute to greater wear of the abrading member and would render it necessary to use high-quality and hence more expensive abrading members.

A concomitant object of the invention is to provide a grinding or polishing machine which may be utilized as a portable machine as well as `a stationary machine, which is constructed and assembled in a way to afford convenient access to its component parts, and which is adapted not only to collect the matter abraded from a workpiece but to simultaneously cool the driving motor which moves the abrading member in an endless path.

With the above objects in View, the invention resides in the provision of a portable grinding or polishing machine which comprises essentially a frame rotatably mounting two spaced wheels or rolls one of which drives and the other of which guides and preferably tensions an endless abrading member, i.e. an abrasive belt. The driving wheel is connected with a motor which is installed in the space formed between the two wheels and whose housing preferably carries a downwardly extending grinding shoe adapted `to deflect the lower run of the belt from a straight path between the wheel-S. The diameters of the wheels and the dimensions of the motor housing are selected in such a way that the upper run of the endless abrasive belt may extend in a straight line from the guiding wheel to the driving Wheel, i.e. that the upper run of the belt is not deected by the motor housing. Owing to such construction, the center of gravity of my improved machine is extremely low which insures better guidance along the surface of a workpiece. In addition, the machine is of very simple construction since it requires only two wheels for properly guiding and advancing the endless belt. The exact position of the center of gravity is determined by the position of the motor whose shaft is preferably parallel with the wheel shafts and is preferably located in or close to the common plane of said wheel shafts. Such arrangement is of considerable advantage because it simplies the driving connection between the motor shaft and the shaft of the driving wheel. Of course, the diigi Patented Aug. 21, 1962 ice ameters of both wheels need not be the same, and the motor shaft need not necessarily be parallel with the wheel shafts.

As stated before, the grinding shoe is preferably mounted directly on and extends downwardly from the lower portion of the motor housing. Such construction allows for further reduction in 4the dimensions of the grinding machine.

Since the upper run of the endless belt does not require additional guiding or deecting rollers, the upper wall of the machine `frame may be formed with a plane upper side or surface so that the machine may be turned upside down and placed on a solid support to serve as a stationary grinding or polishing machine.

Certain other features of the improved machine reside in the provision of special windows in the machine frame and in the grinding shoe which permit observation of coal brushes forming part of the electric driving motor, in the provision of specially constructed cooling and dust collecting fans which may but need not be driven directly by the motor shaft, and in the provision of an adjustably mounted wiper which assist-s the `operation of the dust collecting fan lby preventing the escape of abraded matter from the contines of the machine frame.

In the following description of the Adrawings and in the appended claims, the improved machine will be referred to as a portable grinding machine. However, it will be readily understood that the machine may be utilized as a sander or polisher merely by utilizing a different abrading member.

The novel features which are considered as characteristic for the invention are set forth in particular in the 'appended claims. The invention itself, however, both as to its construction and it-s method of operation, together with additional objects and advantages thereof, will be best understood from Ithe following detailed description of -a specific embodiment when read in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a portable grinding machine embodying my invention;

FIG. 2 is an enlarged side elevational view of the grinding machine; and

FIG. 3 is a section taken substantially along the line lII-I-II of FIG. 2, as seen in the direction of arrows.

Referring now in greater detail to the illustrated embodiment, the portable grinding machine comprises a frame `10 including a side wall 11, an end wall 12 and an upper wall 13. The end wall 12 is connected to or is integrally formed with a handle 15 supporting an internal switch 16 which latter is utilized for starting or arresting the electric driving motor 18. The motor comprises a housing 19 which, as best shown in FIG. 3, may be integral with :the side w-all 11 of the machine frame 10. The motor comprises two carbon brushes 2t), 21 which are located in an inclined plane a-a indicated in FIG. 2.

The driving shaft 23 of the motor 18 carries a spur gear 24 which meshes with an intermediate gear 26 rotatably mounted in the side wall 11, the gear 26 meshing with a driven spur gear 27 `on Ithe shaft 28 of a driving wheel or roll 30. The shaft 28 extends through and is journaled in the side wall 11. At the :opposing side of Ithe motor housing `19, the `side wall 11 rotatably supports the shaft 33 of a belt tensioning and guiding wheel 32. A schematically indicated tensioning assembly 35 constantly biases the shaft 33 in a direction away from tlie `shaft 28, i.e. the tensioning wheel 32 is constantly biased in a direction away from the motor housing 19 whereby the endless abrading member, i.e. a belt 36 which is mounted for travel. about the wheels 30, 32, remains under requisite tension. It will be readily understood that the belt tensioning assembly 35 may be space42 provided at another point of the machine; for example, such modiiied tensioning assembly may comprise a 1springbiased yroll which engages with the upper run 60 or with the lower run 63 of the abrasive belt 36. In such event, the wheel 32 merely guides the belt 36 in its travel along the upper and lower :sides of the motor housing 19. Alternately, the grinding shoe 38 which is illustrated as an integral part and extends from the lower portion of the motor housing 19, and which bears against the lower run 63 of the belt 36, may be resiliently mounted on the motor housing 19 and the tensioning a-ssembly 3S omitted.

The exposed outer side of the side wall 11 supports two fan or ventilator casings 4l), 41 as well as a partition 42 which separates the casing 40 from the casing 41. The interior of the casing 51 communicates with a discharge pipe 43 which removably supports a dust collecting bag 45. This pipe 43 may consti-tute a second handle which is grasped by an opera-tor who desires to transfer the machine to another location. As is clearly shown in FIG. 2, all rigid components of the grinding machine are mounted below the level of the upper wall 13 whereby the machine may be turned upside down and the exposed upper side lof wall 13 placed onto a solid support. In such position, the machine may be utilized as a 4stationary grinder.

The motor shaft 23 is directly connected with two c-oaxial fans 48, 49 which are rotatable in the fan casings 40, 41, respectively. The fan 48 is utilized for drawing cooling air through the intake apertures 50 in the front wall of the motor housing 19, the cooling air passing through said housing and being discharged through the discharge aperture 2 in the fan `casing 40. The second fan 49 is utilized for withdrawing abraded matter, i.e. dust particles, from the space or compartment partially enclosed by walls 11, 12 rearwardly of the shoe 38 and driving wheel 30. In order to improve the ydust collecting action of Athe fan member 49, there is provided a scraper or wiper 54 which is adjustably iixed to the lower edge of the end wall 12 by a series of screws 53. The free lower edge of the wiper 54 -is located in the plane of the underside 55 of the shoe 38 and more particularly in the plane of that zone of the abrasive belt 36 which passes beneath the shoe 38'. The abraded matter is withdrawn through a cutout 58 formed Iin the side wall 11 which communicates with the 4interior of fan casing 41 whence the dust particles travel through the `discharge pipe 43 and into the bag 45. Tlte driving wheel 30 rotates in a clockwise direction so that the Alower run 63 automatically advances matter removed from a workpiece W in a direction tow-ard the cutout 58.

It will be seen that the upper run 60 of the flexible belt 36 is free to pass tangentially from the driving wheel 39 and in a straight path directly to the guiding wheel 32, and that the lower run 63 is free to pass from the idler wheel 32 beneath the underside 55 of the shoe 38 and directly to the driving wheel 30, the motor housing 19 being received in the space formed between the runs 6%, 63 and wheels 30, 32. As is shown in FiG. 2, there is a small clearance b between the upper run 60 and the upper side of the motor housing 19. The shoe 38 projects downwardly and beyond the tangential plane common to the wheels 30, 32 so that the shoe 38 deiects the lower run 63 in downward direction, the belt passing along the underside 55 of the member 3S. In other words, the portions of the lower run 63 which extend between the wheels 30, 32 and the underside S5 of the shoe 3S are inclined with respect to that zone which travels beneath the member 38. The inclination of such belt portions may be varied by utilizing wheels of different diameters. It is preferred to mount the shoe 38 in such manner that it extends only slightly beyond the common lower tangential plane of wheels 30, 32 because such arrangement lowers the center of gravity of the machine.

FIG. 1 shows a window 65 in the upper wall 13 of the machine frame 10. This window is preferably closed by a removable transparent pane 65a which permits observation of the abrasive belt 36. It is preferred to provide the window at such a point that the window permits simultaneous observation and, upon removal of pane 65a, necessary adjustments in the position of the brush 20. As stated before, the brushes 20, 21 are located in the inclined plane a-a which is shown in FIG. 2. Adjustments of the lower brush 21 are made possible by the provision of a second window (not shown) in the grinding shoe 3S.

It will be noted that the axes of wheels 30, 32 and the axis of the motor 1S are located in a common plane and are parallel with each other. The diameters of and the distance between the wheels 30, 32 should be selected in such a way that the motor housing 19 can be readily accommodated in the space between the runs 60, 63 of the abrasive belt 36. lf the portable machine utilizes a slow-running motor, such as an `alternating-current shunt motor or a polyphase induction motor, it may be advisable to drive the fans 48, 49 at a higher speed through a suitable intermediate gearing, i.e. the fans 48, 49 need not be coupled directly to the motor shaft 23. For example, the common shaft of fans 48, 49 may be driven by one or more additional gears (not shown) which mesh with the intermediate gear 26; by proper selection of the Adiameter of such additional gear or gears, the fans may 4be driven at a speed much higher than the speed of the motor shaft 23.

It is also possible to omit the partition 42 between the fan casings 4t), 41 if the fans are constructed and mounted in such a way that the air currents do not interfere with each other. It is further possible to utilize a single fan which is provided with two sets of blades to generate two different currents of air for the cooling of electric motor 18 and for the evacuation of abraded matter, respectively.

Without further analysis, the foregoing will so -fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and speciic aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as. new and desired to be secured by Letters Patent is:

1. In a portable grinding machine, in combination, a frame including a single elongated side wall; a pair of spaced wheels rotatably mounted in opposite longitudinal end portions and located at one side of said side wall; motor means mounted at substantially the same level and intermediate said wheels at said one side of the side wall and having a driving shaft extending through and to the other side of said side wall, the axis of said shaft parallel with the axes of said wheels; a driving connection between said motor means and one of said wheels; an endless abrading band mounted on and extending about said wheels; a rst and a second casing mounted on and 1ocated at the other side of said side wall; motor-cooling first fan means mounted in said rst casing; and dustevacuating second fan means mounted in said second casing, said first and second fan means coaxially connected with said driving shaft so as to be driven by said motor means when the motor means drives said one wheel to advance said abrading member about said wheels.

2. In a portable grinding machine, in combination, a frame including a single elongated side wall; a pair 0f spaced wheels rotatably mounted in opposite longitudinal end portions and located at one side of said side wall; motor means mounted at substantially the same level and intermediate said wheels at said one side of the side wall and having a driving shaft extending through and to the other side of said side wall, the axis of said shaft parallel with the axes of said wheels; an endless abrading band mounted on and extending about said wheels; a first and a second casing mounted on and located at the other side of said side wall; motor-cooling first fan means mounted in said first casing; dust-evacuating second fan means mounted in said second casing, said first and second fan means coaxially connected with said driving shaft; and a driving connection between said driving shaft and one of said wheels, said connection located between said side wall and said casings, said first and second fan means driven by said motor means when the motor means drives said one wheel to advance said abrading member about said Wheels.

3. In a portable grinding machine, in combination, a frame including a single elongated side wall and an upper wall, said upper wall having a substantially flat upper side; a pair of spaced wheels rotatably mounted in opposite longitudinal end portions and located at one side of said side wall and beneath said upper wall; motor means mounted intermediate said wheels at said one side of the side wall and beneath said upper wall, said motor means having a driving shaft extending through and to the other side of said side wall, the axis of said shaft parallel with the axes of said wheels; a driving connection between said motor means and one of said wheels; an endless abrading band mounted on and extending about said wheels beneath said upper wall; a first and a second casing mounted on and located at the other side of said side Wall beneath said upper wall; motor-cooling first fan means mounted in said first casing; and dustevacuating second fan means mounted in said second casing, said rst and second fan means coaxially connected with said driving shaft so as to be driven by said motor means when the ymotor means drives said one wheel to advance said abrading member about said wheels.

4. In a portable grinding machine, in combination, a frame including a single elongated side wall and an end wall extending from one side of and located at one longitudinal end of said side wall, said end Wall comprising outwardly extending handle means; a first and a spaced second wheel, said wheels rotatably mounted in opposite longitudinal end portions and located at said one side of said side wall, said first wheel inwardly adjacent to said end wall; motor means mounted at substantially the same level and intermediate said Wheels at said one side of the side wall and having a driving shaft extending through and to the other side of said side walt, the axis of said shaft parallel with the axes of said wheels; a driving connection between said motor means and one of said wheels; an endless abrading band mounted on and extending about said wheels; a first and a second casing Imounted on and located at the other side of Said side wall; motor-cooling rst fan means mounted in said first casing; and dust-evacuating second fan means mounted in said second casing, said first and second fan means coaxially connected with said driving shaft so as to be driven by said motor means when the motor means drives said one wheel to advance said abrading member about said wheels.

5. In a portable grinding machine, in combination, a frame including a single elongated side wall; a pair of spaced wheels rotatably mounted in opposite longitudinal end portions and located at one side of said side wall; motor means mounted at substantially the same level and intermediate said wheels at said one side of the side wall and having a driving shaft extending through and to the other side of said side Wall, the axis of said shaft parallel with the axes of said wheels; a driving connection between said motor means and one of said wheels; an endless abrading band mounted on and extending about said wheels; a first and a second casing mounted on and located at the other side of said side wall, one of said casings comprising a rigid discharge pipe constituting handle means for said machine; motor-cooling first fan means mounted in said first casing; and dust-evacuating second fan means mounted in said second casing, said first and second fan means coaxially connected with said driving shaft so as to be driven by said motor means when the motor means drives said one wheel to advance said abrading member about said wheels.

6. In a portable grinding machine, in combination, a frame including a single elongated side Wall; a pair of spaced wheels rotatably mounted in opposite longitudinal end portions and located at one side of said side Wall; motor means comprising a housing having a lower portion and mounted at substantially the same level and intermediate said wheels at said one side of the side wall, said motor means comprising a driving shaft extending through and to the other side of said side wall, the axis of said shaft parallel with the axes of said Wheels; grinding shoe means connected to the lower portion of said housing; a driving connection between said motor means and one of said wheels; an endless abrading band mounted on and extending about said wheels and said grinding shoe; a first and a second casing mounted on and located at the other side of said side wall; motorcooling first fan means mounted in said first casing; and dust-evacuating second fan means mounted in said second casing, said first and second fan means coaxially connected with said driving shaft so as to be driven by said motor means when the motor means drives said one wheel to advance said abrading member about said wheels.

References Cited in the file of this patent UNITED STATES PATENTS 669,577 Eck Mar. 12, 19011 1,951,105 Myers Mar. 13, 1934 1,969,318 Myers Aug. 7, 1934 2,000,784 Myers May 7, 1935 2,069,502 Myers Feb. 2, 1937 2,178,865 Swan Nov. 7, 1939 2,251,442 Emmons Aug. 5, 1941 2,275,356 Funk Mar. 3, 1942 2,483,720 Asbury Oct. 4, 1949 2,499,190 Holmgren Feb. 28, 1950 2,718,735 Hamilton Sept. 27, 1955 2,774,198 Emmons Dec. 18, 1956 2,844,834 Nishioka July 29, 1958 FOREIGN PATENTS 40,983 Netherlands .lune 15, 1937 

